The present invention relates generally to techniques and devices for repair of cartilage defects, and specifically to techniques and devices for repair of articular cartilage defects, and particularly to techniques and devices for repair of articular cartilage defects utilizing cell grafts secured in the articular cartilage deficiency utilizing a carrier formed from biodegradable material such as polylactic acid.
The successful repair of articular cartilage defects has eluded clinical medicine and has motivated the investigation of the use of organic and inorganic materials such as collagen matrices (see U.S. Pat. No. 4,846,835), carbon fibers, polyvinyl alcohol sponges, and acrylateamide sponges for the repair of osteochondral defects. The biological acceptability rates resulting from the use of these materials have remained low; however, some promising results have emerged and have encouraged further investigation into the use of synthetic materials for the repair of osteochondral defects.
Polylactic acid, a high-molecular-weight polymer of the cyclic diester of lactic acid, has been utilized as suture material, as surgical dressing following dental extraction, and as surgical rods, plates, and screws. Polylactic acid has several advantages as a biodegradable prosthetic material. It is a nontoxic workable material which can be manufactured into a spectrum of forms with different physical characteristics; it elicits minimal immunological or inflammatory response and has good tissue compatibility; it allows the gradual ingrowth of fibrous connective tissue; and it undergoes hydrolytic deesterification to lactic acid, a normal metabolite of carbohydrate metabolism. The use of polylactic acid by itself has been investigated for the repair of articular defects in rabbits such as reported in Reconstruction of Rabbit Knee Articular Defects with a Polylactic Acid Matrix, R. D. Coutts et al., Orthopedic Research Society, Feb. 5-8, 1990.
It has also been found that the repair of articular cartilage lesions can be enhanced by the transplant of cells having the ability to differentiate into cartilage cells, i.e. marrow, periosteal or perichondrial cells and that will proliferate and produce a matrix that will replace hyaline articular cartilage. Specifically, periosteal grafts have been sutured to the end of a polylactic plug such as reported in The Use of Polylactic Acid Matrix and Periosteal Grafts for the Reconstruction of Rabbit Knee Articular Defects, H. P. von Schroeder et al., Journal of Biomedical Materials Research, Volume 25, 329-339 (1991). The source of cells is carried by and locked into place in the lesion by the polylactic plug which serves as a template for bone formation if it is in contact with bone tissue. The biodegradable device utilized in the investigations reported above was formed of polylactic acid and was of the type shown and described in U.S. Pat. No. 4,186,448 (which is hereby incorporated herein by reference).
The cells carried by the biodegradable device are the mediators of repair tissue and must become attached at the site of repair in order to effect that repair. Thus, a need exists for enhancing the attractiveness of the biodegradable device for cellular attachment at the site of repair. Further, a need exists for facilitating the attachment to the biodegradable device of free cells which act as the source of precursor cells for the production of connective tissue.